2 Answers
2

You don't need the source to resign the app. But you have to have Apple Developers Account and create AppID, AppStore provisioning profile e.t.c. Basically perform all the steps for publishing to the AppStore.

Take a look on www.aironapp.com, it provides resigning functionality plus it can submit to the AppStore for you.

Yes, it is possible to resign an ipa. The one drawback I have found is that I am not able to change the bundle ID of the ipa.

As Alexspott mentions you will need to have an Apple Developers Account, have created an AppID that matches the ipa's bundle ID (If you aren't able to register the App ID to match the bundle ID exactly, you could use a wildcard app ID as long as your app isn't using Push Notifications or In App Purchases), have a valid Certificate, and generate a provisioning profile for this App ID and Certificate.